H - Electricity – 04 – N
Patent
H - Electricity
04
N
354/67
H04N 1/41 (2006.01) H04N 1/417 (2006.01)
Patent
CA 1290852
METHOD AND APPARATUS; FOR BLOCK CODING VERTICAL MODE CODES FOR ENHANCED COMPRESS ION OF IMAGE DATA ABSTRACT OF THE DISCLOSURE A method and apparatus for improving the per- formance of data compression processes, such as rela- tive address coding, CCITT standard facsimile process- es, and similar two-dimensional image coding processes, by block coding one or more of the vertical mode codes produced by these processes. The performance of data compression processes is improved by representing one or more sequences of vertical mode code words with a single block code word. A reference scan line is pref- erably selected from among a plurality of previous scan lines, for example, the immediately preceding ten scan lines, for two-dimensional image coding. The previous scan line which is most similar to the current scan line to be coded is selected as the reference scan line. The selected reference scan line is then fed with the current scan line to be coded to a two-dimensional data compression coding process so as to yield a first tier of data compression. The image data are preferably checked during the two-dimensional data compression coding process for a predetermined run of a given ver- tical mode code, and a preselected block code is substi- tuted if the predetermined run of the given vertical mode code appears so as to yield a second tier of data compression. Preferably, eleven consecutive vertical offset zero code words are represented by a single block code word. This provides enhanced data compression and reduces the amount of image data stored or trans- mitted and concomitantly lowers the cost for operation of the image data storage or transmission apparatus.
542780
Drain Frederick L.
Henderson Alex
Roberts Larry
Fetherstonhaugh & Co.
Netexpress Systems Inc.
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